Who said "The greatest weapon is the conviction in one's own heart."?

This quote is attributed to Leonidas I.

The greatest weapon is the conviction in one's own heart. - Leonidas I

"The greatest weapon is the conviction in one's own heart."

Leonidas I Power

King Warrior Ancient Greece 540–480

"This is Sparta!"

"Spartans! Tonight we dine in hell!"

"A man's true measure is taken not in a moment of comfort and convenience, but in a moment of challenge and adversity."

"Freedom isn't free, it requires sacrifice and courage."

"Power without control is just destruction."

"Power is not about control, it's about influence"

"The world doesn't need me to be the hero. It just needs me to be dangerous."

"The claws come out when I need them to."